Christ founded only one Church —his Church— on Peter, with the guarantee of indefectibility in the face of the persecutions, divisions and obstacles of every kind which she would encounter in the course of history (cf. Mt 16:18). Therefore, only one Church exists, which we confess in the Creed as "one, holy, Catholic and apostolic".

The Second Vatican Council, in n. 8 of the Dogmatic Constitution Lumen Gentium, stated that "this Church, constituted and organized as a society in this present world, subsists in (subsistit in) the Catholic Church, governed by the Successor of Peter and by the Bishops in communion with him, although (licet) many elements of sanctification and truth can be found outside her structure; such elements, as gifts properly belonging to the Church of Christ, impel towards Catholic unity".

As is well known, this famous expression "subsistit in" was subsequently the object of many and contradictory interpretations. The notion became quite widespread that the Council had not wanted to adopt as its own the traditional statement according to which the Church of Christ is (est) the Catholic Church —as was stated in the preparatory schema- so as to be able to say that the Church of Christ subsists also in Christian communities separated from Rome.

In reality, however an analysis of the Council proceedings leads to the conclusion that "[t]he phrase subsistit in is intended, not, only to reconfirm the meaning of the term est, that is, the identity of the Church of Christ with the Catholic Church. Above all, it reaffirms that the Church of Christ, imbued with the fullness of all the means instituted by Christ, perdures (continues, remains) forever in the Catholic Church".

This meaning of the term subsistit coincides with the common language of Western culture and is consistent with classical philosophical language from Aristotle to St Thomas: that which exists in itself and not in something else is said to subsist.

"Subsisting is a special case of being. It is being in the form of a subject standing on its own. This is the issue here. The Council wants to tell us that the Church of Jesus Christ as a concrete subject in the present world can be encountered in the Catholic Church. This can occur only once and the notion that subsistit could be multiplied misses precisely what was intended. With the word subsistit, the Council wanted to express the singularity and non-multiplicability of the Catholic Church".

In this Document of the Council, the assertion of the subsistence of Church of Christ in the Catholic Church is followed by the famous phrase about the presence of many elements of sanctification and truth, belonging to the Church, outside her visible structure.

The Congregation for the Doctrine of Faith, already in 1985, in the face of erroneous interpretations, made the following statement in this regard: "...the Council chose the word subsistit precisely in order to make it clear that exists a single 'subsistence' of the Church, while outside her visible structure only elementa ecclesiae exist, which —as elements of the Church—
tend and lead toward the Catholic Church".

More recently, the same Congregation declared: "The interpretation of those who would derive from the formula subsistit in the thesis that the one Church of Christ could subsist also in non-Catholic churches and ecclesial communities is therefore contrary to the authentic meaning of Lumen Gentium".

Subsistence: universal, particular

From the context and the meaning of subsistit in in Lumen Gentium, n. 8, it is evident that this subsistence is predicated of the universal Church. However, at times, the notion of "the Church's subsistence" has been applied in a different sense —not univocal but analogical— to particular Churches as well.

Thus, for example, John Paul II wrote of "particular Churches in which there subsists the fullness of the universal Church" or that the "Catholic Church herself subsists in each particular Church". The fullness of the universal Church can indeed be predicated of every particular Church, in the sense that, in each particular Church, "the Church universal with all her essential elements is made present". Therefore, each particular Church is constituted "in the image of the universal Church" and, in each one, "the one, holy, catholic and apostolic Church is truly present and operative (inest et operatur)".

This fullness of the particular Church, however, does not come from its particularity, but rather from the presence in it of all the essential elements of ecclesiality, including the Primacy of the Successor of Peter and the College of Bishops. Indeed, these elements, though not originating in the particularity of the Churches, are interior to them. In order that such a fullness might exist, the particular Church must be inserted into the universal Communio Ecclesiarum, which in turn is not possible without communion with the Roman See and its Bishop.

However, this ecclesial fullness is not sufficient to predicate the subsistence of the local Church in the sense of Lumen Gentium, n. 8, since subsistence implies not only the presence of all the essential elements of the Church of Christ, but also their indefectible permanence. And no particular Church has such a guaranteed permanence.

Particular Churches may even disappear, as has happened many times in e course of history. In this sense, it is ore accurate to say, with Christus Dominus, that, in a particular Church, the Church of Christ is present and operative (inest et operatur) or that, in the particular Churches, the universal Church exists (exsistit).

Unicity of the Church, existence of non-Catholic Churches

It is important to note that Lumen Gentium, n. 8, in affirming the subsistence of the Church of Christ in the Catholic Church governed by the Successor of Peter and the Bishops in communion with him (and, as already noted, solely in her), refers explicitly to the Church as constituted and organized in this present world, and then immediately adds that outside her visible structure there are many elements of sanctification and truth. This leads us to consider the Church not only in her social dimension, but also in her mystical-sacramental dimension, as the Mystical Body of Christ.

The Second Vatican Council, following the usage that was already traditional, employs the term Church also for those non-Catholic Christian communities that have preserved the episcopate and a valid Eucharist. Regarding the term Church, attributed to these communities, one of the relators in the Commission for the elaboration of the Decree Unitatis Redintegratio explained that it was not their intention to treat the disputed question of what conditions are required for a Christian community to be, in the theological sense, a Church.

It would seem, therefore, that the intention was only to attribute a sociological, or rather honorific, sense to the term when applied to non-Catholic Christian communities. In reality this does not seem to have been the case, because the same Decree on ecumenism — without making explicit all the, conditions required to be a Church — states that "through the celebration of the Eucharist of the Lord in these individual Churches, the Church of God is built up and grows". This expression is to be interpreted in the light of Lumen Gentium, that is to say, in the sense that, in these Churches many elements of sanctification and truth exist which belong to the one Church of Christ (the Catholic Church).

Later doctrinal and magisterial developments on this topic have led to attributing the title of particular Churches, which is certainly of a theological nature, to non-Catholic communities that have preserved the episcopate and the Eucharist. With regard to magisterial texts, the most notable pronouncements on this question have been two Documents of the Congregation for the Doctrine of the Faith: the Letter Communionis Notio of 1992 which stated that these communities "merit the title of particular Churches", and the Declaration Dominus Iesus of 2000 which stated that they are "true particular Churches".

It is easy to see that where Christ is made present in the Eucharistic sacrifice of his Body and his Blood, there the Church is present as the Body of Christ, through which Christ effects salvation in history. However, not any and every form of the Church's operative presence constitutes a particular Church, but only this presence with all its essential elements.

Therefore, for a Christian community to be truly a particular Church, "there must be present in it, as a proper element, the supreme authority of the Church: the Episcopal College 'together with its head, the Supreme Pontiff, and never apart from him' (Lumen Gentium, n. 22)". This might seem an insurmountable obstacle to the possibility of affirming that non-Catholic particular Churches are "true particular Churches", and certainly there is much in this area that calls for deeper study.

One possible path for reflection, however, would be the real presence of the Petrine Primacy (and of the Episcopal College) in non-Catholic Churches, based on the unity of the "one and undivided" episcopate: a unity that cannot exist without the Bishop of Rome. Where, on account of apostolic succession, a valid episcopate exists, the Episcopal College with its Head is objectively present as supreme authority (even if, in fact, that authority is not, recognized).

Furthermore, in every valid celebration of the Eucharist, there is an objective reference to the universal communion with the Successor of Peter and with the entire Church , independent of subjective convictions.

Perhaps it will be possible along these lines to arrive at a deeper understanding of the fact that these comunities, while being separated from Rome, are "true particular Churches". However, it must be remembered that the fact of being not in full communion with the Pope implies a wound in their ecclesiality, which is not only of a disciplinary or canonical nature, but is also related to the not full profession of the Catholic faith. Therefore, what is lacking for a non-Catholic particular Church to be fully a Church is not only a belonging to the visible manifestation (in an exterior sense) of the full Christian communion.

It is necessary to return always to what the Catholic faith teaches about the unicity of the one Church of Christ so as not to overlook another aspect of capital importance: non-Catholic particular Churches are true Churches on account of what is Catholic in them. Their ecclesiality is based on the fact that "the one Church of Christ has an operative presence in them", and they are not fully Churches —their ecclesiality is wounded— because they lack elements proper to the Catholic Church. In other words, recognizing that these communities, which are not in full communion with the Catholic Church, have the character of Churches also means necessarily that these Churches are —in an apparent paradox— portions of the one Church, that is to say, of the one Catholic Church, portions in an anomalous theological and canonical situation. One could say similarly that theirs is a "participated ecclesiality according to an imperfect and limited presence of the Church of Christ".

The ecumenical relevance of these ecclesiological topics is obvious; they still need to be more clearly delineated and studied. The commitment to ecumenism, which the Church neither can nor wishes to relinquish, is not limited to doctrinal aspects.
"But what is most urgently needed is that 'purification of memory', so often recalled ' by John Paul II, which alone can dispose souls to accept the full truth of Christ".
Certainly, obstacles remain, but there is always room for prayer, thanksgiving, dialogue and hope in the action of the Holy Spirit.